Method and System for Producing Reduced Gluten Oat Mixture

ABSTRACT

A method and system is disclosed which uses a combination of optical and mechanical separation processes to remove gluten-containing grains from a mixture of oat kernels.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates generally to a method and system formaking an oat mixture with substantially reduced levels of gluten.

Background

Oat-based cereals are well accepted by consumers. This may be due, inpart, to the widespread publication of the beneficial impact of oat branin providing a healthful lowering of low density lipoprotein cholesterolcomponents in the human system. The oat is a highly nutritious grain,not only in terms of possessing outstanding soluble fiber levels, butalso in terms of the richness of its protein, mineral, and lipidcontent, as well as other nutritive components.

In recent years, there has been a rise in consumer interest in foodproducts that do not contain gluten. Grain products that contain gluteninclude wheat, barley and rye. Although oats do not contain gluten, oatsare harvested, transported and processed using equipment that is alsoused for wheat, barley and rye. Therefore, oat products canunintentionally include small amounts of gluten-containing grains, butstill enough to render an oat-based food product not technically“gluten-free” according to government or food industry standards.Removing unwanted grains from an oat mixture is difficult due to thesimilarity in size, shape and appearance between oats andgluten-containing grains.

SUMMARY OF THE INVENTION

The present invention generally provides a system and method forremoving unwanted grains from an oat kernel mixture. Incoming oats thathave been harvested and transported to an oat processing facility areaspirated and screened initially. Large impurities such as corn andsoybeans, as well as material smaller than the typical oats, such asweed seeds and other grains are removed. Lighter material like chaff andimmature oats are removed with aspiration. The resulting oat mixture ismechanically cleaned in a first mechanical cleaning step by feeding theminto an indented rotating cylinder cleaner. The cleaned oat stream isthen mechanically cleaned again in a second mechanical cleaning step byfeeding the cleaned oat stream into a second indented cylinder cleaner.In a preferred embodiment the indentation diameter is between about 6and 7 millimeters.

The second cleaned oat stream is then destoned by feeding it into anangled, oscillating table that is rotating about a central axis thatpasses air up through the oat stream, causing heavy material (mostlydirt and rocks, with some wheat removal) to travel up the table andlighter matter (oats) to travel down the table and into the next step inthe process.

The destoned stream is then fed into an optical sorter configured toexpel gluten-containing grains from the oat stream. In a preferredembodiment, the optical sorter comprises at least one bichromatic camerathat operates in the visible light spectrum, and at least onebichromatic camera that operates in the infrared spectrum. When thecameras detect a non-oat grain, a gas expeller fires, rejecting thenon-oat grain from the stream. The optically sorted oat stream may thenbe optionally stored for a time in storage bins before proceeding to thenext steps.

The next step in the process is a dehulling step, which removes the oatgroat from the hull. This step is known in the art. The de-hulled oatsare then optically sorted again, using equipment that is functionallysimilar to the optical sorting equipment used prior to the dehullingstep, although less sophisticated optical sorting equipment may be usedbecause the target for removal at this step is groats that are stillattached to the hull. The de-hulled then optically sorted oat stream ismechanically screened to remove a substantial portion of the barleygrains remaining in the oat stream. The mechanical screening equipmentcomprises a sieve that catches the barley but lets the oat groats passthrough and proceed on to a kilning step, which is known in the art.

The next step in the process is a groat separation step, which usesequipment that is functionally similar to the equipment used to destonethe mechanically cleaned oat stream. This step separates the groats intoone or more oat grade streams, each of which passes through a thirdoptical sorting step using equipment that is functionally similar to theprevious two optical sorting steps, but is configured to identify andremove barley grains that have passed through the kilning step. Theoptically sorted oat stream may then optionally be further processed,such as by a flaking or cutting step, and optionally mixed with otheringredients such as flavoring ingredients, and optionally packaged.

In one embodiment, a method for processing oat kernels comprises: priorto a de-hulling step for an oat kernel stream, at least two of thefollowing: mechanically cleaning the oat kernel stream by passing theoat kernel stream through a first rotating cylinder comprising aplurality of indentations on an inner surface of the first cylinder;density separating the oat kernel stream by passing the oat kernelstream over at least one oscillating gravity separation table;mechanically screening the oat kernel stream using at least one meshscreen to allow a mechanically screened oat kernel stream to passthrough the mesh screen or capturing a mechanically screened oat kernelstream on the mesh screen, or both; optically sorting the oat kernelstream by passing the oat kernel stream through an optical sorter thatuses at least one camera to identify at least one non-oat constituent ofthe oat kernel stream, and a gas expeller to reject any identifiednon-oat constituent into a waste stream; after the de-hulling step butbefore a kilning step for a de-hulled oat stream, at least two of thefollowing: mechanically cleaning the de-hulled oat stream by passing thede-hulled oat stream through a second rotating cylinder comprising aplurality of indentations on an inner surface of the second cylinder;density separating the de-hulled oat kernel stream by passing thede-hulled oat kernel stream over at least one oscillating gravity table;mechanically screening the de-hulled oat stream using at least one meshscreen to allow a mechanically screened de-hulled oat stream to passthrough the mesh screen or capturing a mechanically screened de-hulledoat stream on the mesh screen, or both; and optically sorting thede-hulled oat stream by passing the de-hulled oat kernel stream throughan optical sorter that uses at least one camera to identify at least onenon-oat constituent of the de-hulled oat stream, and a gas expeller toreject any identified non-oat constituent into a waste stream; and aftera kilning step for a kilned oat stream, at least two of the following:mechanically cleaning the kilned oat stream by passing the kilned oatstream through a third rotating cylinder comprising a plurality ofindentations on an inner surface of third cylinder; density separatingthe kilned oat stream by passing the kilned oat stream over at least oneoscillating gravity separation table; mechanically screening the kilnedoat stream using at least one mesh screen to allow a mechanicallyscreened kilned oat stream to pass through the mesh screen or capturinga mechanically screened kilned oat stream on the mesh screen, or both;optically sorting the kilned oat stream by passing the kilned oat streamthrough an optical sorter that uses at least one camera to identify atleast one non-oat constituent of the kilned oat stream, and a gasexpeller to reject any identified non-oat constituent into a wastestream; wherein the method produces an oat stream with a final glutencontent which is lower than an initial gluten content of the oat kernelstream.

In one embodiment, the non-oat constituent is a gluten-containing grain.In another embodiment, prior to the de-hulling step, at least three ofthe mechanically cleaning, density separating, mechanical screening oroptically sorting steps occur. In still another embodiment, after thedehulling step but before the kilning step, at least three of themechanically cleaning, density separating, mechanical screening oroptically sorting steps occur. In another embodiment, after the kilningstep, at least three of the mechanically cleaning, density separating,mechanical screening or optically sorting steps occur.

In another embodiment of the invention, a system for removing at leastone non-oat constituent from an incoming oat kernel stream comprises:prior to de-hulling: a first mechanical screener comprising a firstscreen which allows oat kernels to pass through and captures oat kernelstream constituents larger than oat kernels, or a second screen whichcaptures oat kernels on the second screen and allows oat kernel streamconstituents smaller than oat kernels to pass through, or both the firstscreen and second screen; a first density separator comprising at leastone oscillating table that separates the oat kernel stream into at leasttwo fractions based on density of oat kernel stream constituents; asecond density separator comprising at least one oscillating table thatseparates the oat kernel stream into at least two fractions based ondensity of oat kernel stream constituents; a first mechanical cleanercomprising a first rotating cylinder comprising a plurality ofindentations on an inner surface of the first cylinder; a secondmechanical cleaner comprising a second rotating cylinder comprising aplurality of indentations on an inner surface of the second cylinder;and a first optical sorter comprising at least one bichromatic cameraoperating in the visible light spectrum and at least one bichromaticcamera operating in the infrared light spectrum, wherein the camerasidentify at least one non-oat constituent of an oat kernel stream, and agas expeller which rejects any identified non-oat constituent into awaste stream; after de-hulling and before kilning: a third mechanicalcleaner comprising a third rotating cylinder comprising a plurality ofindentations on an inner surface of the third cylinder; a third densityseparator comprising at least one oscillating table that separates ade-hulled oat stream into at least two fractions based on density ofde-hulled oat stream constituents; a fourth mechanical cleanercomprising a fourth rotating cylinder comprising a plurality ofindentations on an inner surface of the fourth cylinder; a secondmechanical screener; and a fifth mechanical cleaner comprising a fifthrotating cylinder comprising a plurality of indentations on an innersurface of the fifth cylinder; and after kilning: a sixth mechanicalcleaner comprising a sixth rotating cylinder comprising a plurality ofindentations on an inner surface of the sixth cylinder; a fourth densityseparator comprising at least one oscillating table that separates akilned oat stream into at least two fractions based on density of kilnedoat stream constituents; and a second optical sorter which rejects atleast one identified non-oat constituent from the kilned oat stream.

In one embodiment, each system component before de-hulling is in series.In another embodiment each system component after kilning is in series.In another embodiment, the indentations on each mechanical cleanercomprise a diameter of between about 6 and 8 millimeters.

The creation of oat-based products using the methods described hereinmay allow manufacturers the ability to label their products as“gluten-free” because they meet industry or government standardsregarding the same. Gluten-sensitive consumers would thus have theoption to purchase and consume oat-based products with far less risk ofgluten contamination.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbe best understood by reference to the following detailed description ofillustrative embodiments when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a flow chart illustrating a first exemplary embodiment of themethod of the present invention;

FIG. 2 is a flow chart illustrating a second exemplary embodiment of themethod of the present invention;

FIG. 3 is a diagrammatic view of an optical sorter which can be used inaccordance with one embodiment of the present invention;

FIG. 4 is a flow chart illustrating a third exemplary embodiment of themethod of the present invention;

FIG. 5 is a flow chart illustrating a fourth exemplary embodiment of themethod of the present invention.

DETAILED DESCRIPTION

Oats are cereal grains suitable for human consumption, commonly in theform of oatmeal. Alternatively, they may be used as an ingredient informing oat-based products, such as granola bars and the like. Oat-basedproducts have recently experienced a resurgence in popularity as aresult of the increasing number of studies documenting health benefitsderived from consuming oats, such as the promotion of healthy heartfunction. However, oat-based products sometimes contain non-trivialamounts of gluten-containing grains because it is difficult to separatesuch grains out from a stream or batch of harvested oats.

Referring now to FIG. 1, incoming oat kernels 101 are first subjected toa first mechanical cleaning step 102. In a preferred embodiment, thefirst mechanical cleaning step uses a rotating cylinder comprising aplurality of indentations on its interior surface to capture and removedirt, other foreign matter, as well as wheat and some barley, from theincoming oat stream. In one embodiment, the rotating cylinder used inthe first mechanical cleaning step. In a preferred embodiment, thediameter of the indentation is between about 6 and 7 millimeters. Oneexample of mechanical cleaning equipment that can be used in accordancewith certain embodiments of the present invention is sold by CimbriaHeid GmbH of Austria.

The oat stream is fed into one end of the rotating cylinder. Wheat andbarley grains (as well as other foreign matter) embed themselves intothe indentations due to gravity at the bottom of the cylinder, and thenfall out of the indentations at a certain point as they rotate up withthe wall of the cylinder. The grains and other foreign matter that fallout of the indentations are collected in a separate stream, whereas theoat stream that passes through the cylinder without falling into theindentations proceeds to the next step.

The mechanically cleaned oat stream is then fed into a second mechanicalcleaning step 104. The equipment used for this step is functionallyequivalent or similar to the equipment used in the first mechanicalcleaning step. Here again, a cleaned oat stream passes through therotating cylinder without getting caught and removed by theindentations. This step removes a second fraction of wheat and barleyfrom the oat stream.

The oat stream is then subjected to a destoning step 106. Destoningprocesses and equipment are known in the art, but generally, in oneexample embodiment, the oat stream is fed into an angled, rotating tablewhich creates a fluidized bed by passing air up through the oat streamas the table is rotated. During this process, heavy material travels upthe table and is collected in a waste stream, and the lighter oatmaterial passes down the table and is collected in a destoned oatstream. Other processes that separate the oat stream into fractionsbased on density may also be used in accordance with the presentinvention.

The destoned oat stream is then subjected to a first optical sortingstep 108. Referring now to FIG. 3, therein is depicted a diagrammaticrepresentation of one embodiment of an optical sorter 300 that can beused in accordance with the present invention. As shown therein, an oatstream 302 is fed into the inlet 304 of the sorter, which is typicallyat or near the top of the device. The stream is thinned and fed in acontrolled manner down a chute 306 where the oats and other constituentsof the oat stream fall down and into the line of sight of four cameras.

In a preferred embodiment, the cameras are bichromatic cameras, with atleast one operating in the visible light spectrum 312 and 314, and atleast one operating in the infrared light spectrum 308 and 310.Bichromatic cameras more accurately detect non-oat constituents thanmonochromatic cameras because color differences between oats and othergrains are difficult to discern. If any camera detects a non-oatconstituent in the oat stream, expeller 320 shoots a stream of air orother gas at the identified non-oat constituent, causing it to beremoved from the oat stream and collected in a waste stream 322.Although a minor fraction of oats may also be expelled with the non-oatconstituents, substantially all of the oats in the oat stream passthrough the optical sorter and are collected in an optically sorted oatstream 324. In a preferred embodiment, the main targets for removal atthis optical sorting step are at least one of wheat and rye grains.

The optically sorted oat stream may optionally be stored 110 and/ortransported, or a portion of it may be recycled back to any of theprevious steps, before being subjected to a dehulling step 112.Dehulling of oats is a process that is known in the art. It generallyinvolves impacting the oat kernels with a surface with enough force toseparate the oat groat from the hull. The denser oat groat is thenseparated from the lighter hull, which comes off the process as a wastestream. Oat groats are the primary oat fraction that is used for humanconsumption.

The dehulled oat groat stream 114 is then subjected to another opticalsorting step. The equipment used for the second optical sorting step maybe substantially similar to the equipment used in the first opticalsorting step. However, monochromatic cameras and fewer cameras may beused in this step. The primary target for removal at this point in theprocess is groats which have not been successfully separated from thehull. Optical sorting systems can more easily distinguish a separatedgroat from a groat with the hull attached. The waste stream from thisoptical sorting step may be recycled, in one embodiment, back to thedehulling step.

The optically sorted groat stream is then optionally subjected to amechanical screening process 116 to remove barley primarily, but alsosome wheat. In the mechanical screening process, the groat stream ispassed through at least one sieve, which is sized such that groats passthrough the sieve and barley and some wheat grains are retained on thesieve. In a preferred embodiment, the mesh opening size of the sieve orsieves used in this step can range from 2.4 to 2.7 millimeters,inclusive of all intervening ranges. Furthermore, the screens used tomechanically separate the barley from the groats at this step may be anyshape practicable, including flat screens or cylindrical screens.

The groat product stream emerging from the mechanical screening step isthen subjected to a kilning step 118. During kilning, the groats arestabilized against off-flavors and rancidity by subjecting them to heatand moisture treatments to denature the enzymes (primarily lipase)responsible for breaking down the lipids present in the groat. Kilningprocesses are known in the art and any known or developed kilningprocess can be used in accordance with the present invention.

The kilned groats may then be optionally sorted 120 into one or more oatgrades 122 and 124 based on density. Equipment suitable for this step issimilar to the equipment used for the destoning step described above.

The groats are then subjected to a final, third optical sorting step126, which uses equipment that is substantially similar in function tothe equipment used in the first and second optical sorting step. In thisstep, the main target for removal is barley because it is easier for theoptical sorting equipment to discern a groat from a barley grain afterthey have passed through the kilning process.

The optically sorted groats may optionally then be cut, flaked, milled,or screened, or any combination thereof, according to the preference ofa practitioner of the present invention.

An alternative exemplary embodiment of the inventive oat processingmethod is disclosed in FIG. 2. There, incoming oats 101 are subjected totwo mechanical cleaning steps 202, 204 using the indented cylindersdescribed above, and another mechanical cleaning step 206 using agravity table as described above. The cleaned oats are optically sorted208, and temporarily stored in storage bins 210. The oat mixture issubjected to a dehulling step 212 and second optical sorting step 214before kilning 118. The kilned oat mixture is then subjected to agravity table separation step 216, and the output is separated into atleast two different grades of oats 218 and 220. Those oat gradefractions are mechanically cleaned and optically sorted again to removeany barley and wheat remaining. The oats can then be flaked 228 or 230,or subjected to further processing as desired.

FIG. 4 depicts another embodiment of the inventive oat processing systemand method. As shown therein, incoming oats 101 are subjected to amechanical separation step 402 by passing the oat mixture through ascreen, similar to the mechanical screening step 116 shown in FIG. 1.The mechanical screening step may be used to remove larger corn, wheatand barley grains, and allow the smaller oat grains to pass through tothe next processing steps. The mechanical screening step may also beused to filter finer particles from the incoming oat mixture bycapturing oat kernels on top of a screen that allows finer particles topass through. The mechanical screening step may also both screen largerparticles out of the incoming oat stream and screen finer particles. Thescreened oat mixture is then separated using a gravity table densityseparation step 404, similar to the density separation step 120 shown inFIG. 1. This density separation step may be repeated 406 with similarequipment. Next, the oat mixture is mechanically cleaned by passing itthrough at least one rotating indented cylinder 408 and 410, similar tothe mechanical cleaners described above for FIG. 1 reference numerals102 and 104. In a preferred embodiment, the diameter of the indentationsin the first mechanical cleaning step 408 is between 6 and 8 mm, andmost preferably 8 mm. In a preferred embodiment, the diameter of theindentations in the second mechanical cleaning step 410 is between 6 and8 mm, and most preferably 6.75 mm.

In the method and system described in FIG. 4, the mechanically cleanedoats are optically sorted 412 using equipment as described above withrespect to steps 108 or 114 in FIG. 1. The optically sorted oats thenpass to a dehulling step 414 as described above for step 112 in FIG. 1.The dehulled oats are then mechanically cleaned 416 using a rotatingindented cylinder, as described herein above. Preferably, theindentation diameter used in this step is between 6 and 8 mm, and morepreferably about 8 mm. The oats that pass through the mechanicalcleaning cylinder at 416 without getting caught in the indentations goto a density separation step 418 similar to step 404. The oat fractionthat emerges from the density separation step 418 is subjected tokilning 118. The waste stream from density separation step 418 andmechanical cleaning step 416 is passed through a mechanical screen, andthe pass through stream of oats is also subjected to kilning 118.

The kilned oats are then aspirated 422 to remove light materials fromthe kilned oats and subjected to another mechanical cleaning step 424using an indented rotating cylinder. The indentation diameter at step424 is preferably between 6 and 8 mm. The oats that pass through therotating cylinder are subjected to another gravity table densityseparation step 428 and optical sorting step 430. The stream of oatsemerging from the optical sorter 430 are gluten-free oats. The wastestream from steps 424, 428 and 430 are collected into a non-gluten-freeoat stream, which can be consumed by humans who are tolerant of gluten.The oats may optionally be intermediately stored 434 and cut, flaked orpackaged 436, according to the preference of the practitioner of thepresent invention.

FIG. 5 depicts an alternative embodiment of the inventive method andsystem. The process is identical to FIG. 4 until the kilned oats havebeen mechanically cleaned by a rotating indented cylinder at 424.Thereafter, the waste stream from the rotating indented cylinder ismechanically cleaned 502 again by a rotating cylinder with anindentation diameter of between 4.5 and 6 mm, and most preferably 5.0mm. The fraction that passes through the cylinder without being capturedby the indentations is a non-gluten free flour groat stream 504. Thewaste stream from mechanical cleaning step 502 becomes a part of thenon-gluten free oat stream 426.

In other embodiments, the incoming oat streams for the processesdepicted in FIG. 1, 2, 4 or 5 are pre-processed by at least one ofmechanical screening, density separation and mechanical cleaning priorto being processed by the steps shown in those Figures.

The groat stream that emerges from the inventive process and systemcomprises substantially lower amounts of gluten-containing grains thangroat streams produced by known processes. The method and systemdescribed above was tested on incoming oat kernel streams. The targetupper limit for the tests was less than 20 parts per million (ppm)gluten in the final groat stream. The gluten content of a fullyprocessed groat stream was measured 40 times over a 14-hour period afterthe process had reached steady-state, and was found to comprise anaverage gluten content of about 2.63 ppm, with a standard deviation of1.7 ppm. In a separate test, the gluten content of fully processed groatstream was measured 30 times over a 6-hour period after the process hadreached steady-state, and was found to comprise an average glutencontent of about 3.93 ppm, with a standard deviation of 2.92. Based onall of the tests that were run, the applicants herein have statisticalconfidence that less than 1 in 10,000 final oat products made with theprocessed groat stream produced by the inventive system and method wouldcontain more than 20 ppm gluten.

While this invention has been particularly shown and described withreference to preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention.The inventors expect skilled artisans to employ such variations asappropriate, and the inventors intend the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A method for processing oat kernels comprising: prior to a de-hullingstep for an oat kernel stream: mechanically cleaning the oat kernelstream by passing the oat kernel stream through a first rotatingcylinder comprising a plurality of indentations on an inner surface ofthe first cylinder; density separating the oat kernel stream by passingthe oat kernel stream over at least one oscillating gravity separationtable; mechanically screening the oat kernel stream using at least onemesh screen to allow a mechanically screened oat kernel stream to passthrough the mesh screen or capturing a mechanically screened oat kernelstream on the mesh screen, or both; and optically sorting the oat kernelstream by passing the oat kernel stream through an optical sorter thatuses at least one camera to identify at least one non-oat constituent ofthe oat kernel stream, and a gas expeller to reject any identifiednon-oat constituent into a waste stream; after the de-hulling step butbefore a kilning step for a de-hulled oat stream: mechanically cleaningthe de-hulled oat stream by passing the de-hulled oat stream through asecond rotating cylinder comprising a plurality of indentations on aninner surface of the second cylinder; density separating the de-hulledoat kernel stream by passing the de-hulled oat kernel stream over atleast one oscillating gravity table; and mechanically screening thede-hulled oat stream using at least one mesh screen to allow amechanically screened de-hulled oat stream to pass through the meshscreen or capturing a mechanically screened de-hulled oat stream on themesh screen, or both; and after a kilning step for a kilned oat stream:mechanically cleaning the kilned oat stream by passing the kilned oatstream through a third rotating cylinder comprising a plurality ofindentations on an inner surface of third cylinder; density separatingthe kilned oat stream by passing the kilned oat stream over at least oneoscillating gravity separation table; optically sorting the kilned oatstream by passing the kilned oat stream through an optical sorter thatuses at least one camera to identify at least one non-oat constituent ofthe kilned oat stream, and a gas expeller to reject any identifiednon-oat constituent into a waste stream; wherein the method produces anoat stream with a final gluten content which is lower than an initialgluten content of the oat kernel stream.
 2. The method of claim 1wherein the non-oat constituent is a gluten-containing grain. 3.(canceled)
 4. (canceled)
 5. (canceled)
 6. A system for removing at leastone non-oat constituent from an incoming oat kernel stream comprising:prior to de-hulling: a first mechanical screener comprising a firstscreen which allows oat kernels to pass through and captures oat kernelstream constituents larger than oat kernels, or a second screen whichcaptures oat kernels on the second screen and allows oat kernel streamconstituents smaller than oat kernels to pass through, or both the firstscreen and second screen; a first density separator comprising at leastone oscillating table that separates the oat kernel stream into at leasttwo fractions based on density of oat kernel stream constituents; asecond density separator comprising at least one oscillating table thatseparates the oat kernel stream into at least two fractions based ondensity of oat kernel stream constituents; a first mechanical cleanercomprising a first rotating cylinder comprising a plurality ofindentations on an inner surface of the first cylinder; a secondmechanical cleaner comprising a second rotating cylinder comprising aplurality of indentations on an inner surface of the second cylinder;and a first optical sorter comprising at least one bichromatic cameraoperating in the visible light spectrum and at least one bichromaticcamera operating in the infrared light spectrum, wherein the camerasidentify at least one non-oat constituent of an oat kernel stream, and agas expeller which rejects any identified non-oat constituent into awaste stream; after de-hulling and before kilning: a third mechanicalcleaner comprising a third rotating cylinder comprising a plurality ofindentations on an inner surface of the third cylinder; a third densityseparator comprising at least one oscillating table that separates ade-hulled oat stream into at least two fractions based on density ofde-hulled oat stream constituents; a fourth mechanical cleanercomprising a fourth rotating cylinder comprising a plurality ofindentations on an inner surface of the fourth cylinder; a secondmechanical screener; and after kilning: a fifth mechanical cleanercomprising a fifth rotating cylinder comprising a plurality ofindentations on an inner surface of the fifth cylinder; a fourth densityseparator comprising at least one oscillating table that separates akilned oat stream into at least two fractions based on density of kilnedoat stream constituents; and a second optical sorter which rejects atleast one identified non-oat constituent from the kilned oat stream. 7.The system of claim 6 wherein the non-oat constituent comprises agluten-containing grain.
 8. The system of claim 6 wherein each systemcomponent before de-hulling is in series.
 9. The system of claim 6wherein each system component after kilning is in series.
 10. The systemof claim 6 wherein the indentations on each mechanical cleaner comprisea diameter of between about 6 and 8 millimeters.